• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1059-1065
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• 2010

An analysis was conducted to predict the hydraulic performance of a reactor coolant pump (RCP) of SMART at the off-design as well as design points. In order to reduce the analysis time efficiently, a single passage containing an impeller and a diffuser was considered as the computational domain. A stage scheme was used to perform a circumferential averaging of the flux on the impeller-diffuser interface. The pressure difference between the inlet and outlet of the pump was determined and was used to compute the head, efficiency, and break horse power (BHP) of a scaled-down model under conditions of steady-state incompressible flow. The predicted curves of the hydraulic performance of an RCP were similar to the typical characteristic curves of a conventional mixed-flow pump. The complex internal fluid flow of a pump, including the internal recirculation loss due to reverse flow, was observed at a low flow rate.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.195-202
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• 1987

The flow characteristics in the shallow open channel bends are investigated, whose total angles were 30, 60, 90, 120, 150 and 180 in degree, and whose bed frictions were relatively rough(C=30) and smooth(C=60), respectively. The terms analyzed in this study are the water surface profile, the distribution of velocity and the flow direction, relating to the various total angles in the bends. The maximum depth in the bends could be found at the outside section of the location of $15^{\circ}$ local angle from the bend inlet, having no relation to the total angle and bed friction. It is supposed that the path of maximum velocities is especially influenced by the bottom friction when the total angles are bigger than 150 in degree, approximately. The ratio of the superelevation to the velocity head seems to increase as the total angle of the bends increases. The flow direction is skewed to the inner side at the bend inlet, and skewed to the outside at the bend outlet, regardless of their total angles.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1652-1660
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• 1990

Combined radiative-convective heat transfer in a hot gas tube flow has been investigated numerically and experimentally. In the numerical analysis, a standard k-.epsilon. model is used for the evaluation of turbulent shear stresses and spherical harmonics method with the Weighted Sum of Gray Gases Model for the solution of radiative transfer equation. In the experimental study measured are the velocity and temperature of the hot gas flow generated by the propane gas combustion, and tude wall heat flux distribution. Numerical results are compared with experimental ones and it is confirmed that P-3 provides quite reliable results in the analysis of the combined radiation-convection system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.5
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• pp.533-538
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• 2012

In this study, we used an $O_2$-sensitive luminescent dye to measure the $O_2$ concentration of culture media around HeLa cells cultured in a microchannel. $[Ru(bpy)_3]^{2+}$, which dissolves easily in water and which has no phototoxic effect, was used as the $O_2$-sensitive dye. The ratiometric sensing method was applied by introducing calcein as the $O_2$-insensitive dye, in order to overcome the disadvantages of intensity-based sensing. By performing calibration with an amperometric $O_2$ sensor, we could calculate the exact concentration of $O_2$ in the culture media. We applied this technique to measure the $O_2$ concentration around the cultured cells in the microchannel. As expected, the $O_2$ concentration gradually decreased as the cells moved farther away from the channel. This method is expected to be applicable to the investigation of hypoxia, which occurs commonly in scaffolds.

• Journal of Food Hygiene and Safety
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• v.31 no.3
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• pp.201-209
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• 2016

Many atmospheric pollutants including chemical agents, house dust, and microorganisms cause building-related illnesses through respiration in humans. This study was conducted to analyze the profiles of microbial pollutants in air purifiers used in home, office and playschool. Dominant eleven species of microorganisms were isolated and identified in environmental air and air purifiers. Among them, Staphylococcus sp., Micrococcus sp. and Bacillus sp. are the most dominant species. By phylogenetic analysis of the 16S rRNA gene, the dominant bacteria were identified as Staphylococcus epidermidis, Micrococcus luteus and Bacillus epidermidis, respectively. It has been known that these bacterial species are closely related with food spoilage and human infectious disease. Thus, these results indicate that microbial pathogens related with human illnesses through respiration will be contaminated in air purifiers and also need to develop a method to control those of pathogens for human health.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.6
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• pp.769-774
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• 2013

Turbine blades and disc, which are one of the most important rotating parts of a gas turbine engine, are required to have highly efficient performance in order to minimize the total life cycle costs. Owing to these requirements, these components are exposed to severe conditions such as extreme turbine inlet temperatures, high compression ratios, and high speeds. To evaluate the structural integrity of a turbine disc under these conditions, material modeling and finite element analysis techniques are essential; furthermore, shape optimization is necessary for determining the optimal solution. This study aims to generate 2D finite element models of an axisymmetry model and a sector one and to perform thermal-structural coupled-field analysis and contact analysis. Structurally vulnerable areas such as the disc bore and disc-blade interface region are analyzed by a parametric study. Finally, an improved design is provided based on the results, and the necessity of elaborate shape optimization is confirmed.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.615-624
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• 2014

The fin-tube heat exchanger being used for industrial boiler, radiator, refrigerator has been conducted in various studies to improve it's performance. In this study, the characteristics of heat transfer and pressure drop was theoretically analyzed according to longitudinal pitch, location of vortex generator, bump phase and number of the tube surface about the plain fin-tube heat exchanger. The boundary condition for the CFD (Computational Fluid Dynamics) analysis applied with the SST (Shear Stress Transport) turbulence model assumed as the tube surface temperature of 333 K, the inlet air temperature of 423-438 K and the inlet air velocity of 1.5~2.1 m/s. The analysis results indicated that the heat transfer coefficient is not affected highly by the longitudinal pitch, and the heat transfer characteristics was more favorable when the vortex generator was located in front of the tube. Also the bump phase of the tube surface indicated that circle type was more appropriate than serrated type and triangle type in the characteristics of heat transfer and pressure drop, and the sixteen's bump phase of circle type was most favorable.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.7
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• pp.574-579
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• 2016

Grid systems used in previous studies were determined to be valid only if the length between the perpendiculars in a model ship was in the range of 6-8 m, and the maximum dynamic trim angle was smaller than $1^{\circ}$. The application of the grid system to a small fishing boat can create numerical instability because the dynamic trim of small boats is generally larger than $3^{\circ}$, and their Froude numbers are in the range of 0.3-0.8. In the present study, resistances of a small fishing boat were stably obtained by reducing the length between the center of buoyancy and the inlet boundary of the numerical domain, and by refining grid cells vertically in a region that would be swept by a free surface. The effective power of the small fishing boat was predicted based on the ITTC-1978 two-dimensional analysis. By using the results of previous towing tank tests, the coefficient of quasi-propulsive efficiency and the brake horsepower at a design draft were calculated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1272-1278
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• 2014

In this experimental study for the current growing offshore wind, a wind tunnel test was conducted to examine the performance of the vertical-type cross-flow wind turbine power generation system. Due to the limited size of the test section of the wind tunnel, the inlet guide vane of the original wind power generation was scaled down to about 1/5 and the turbine impeller diameter was also reduced to 1/2 of the prototype impeller. The number of the impeller blade is another important parameter to the output power of the wind power generation system and the number was varied 8 and 16. From the analysis of the experimental result, the output brake power of the model wind turbine was measured as 278watts with the 16-blade at 12 m/s of the rated wind speed and the rated brake power of the prototype wind turbine is calculated to 3.9kW at the rated operating condition.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.7
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• pp.79-88
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• 2006

In the present paper, the swirl flow structure and flame characteristics of turbulent premixed combustion in a model gas turbine combustor are investigated using large eddy simulation(LES). A G-equation flamelet model is employed to simulate the unsteady flame behavior. When inlet swirl number is increased, the distinct flow structures, such as the shapes of corner recirculation and center toroidal recirculation zone, are observed and the flame length is shorted gradually. Also, the phenomena of flashback are identified at strong swirl intensity. In order to get the accurate description of unsteady flame behavior, the predictive ability of the acoustic wave in a combustor is primarily evaluated. It is found that the vortex generated near the edge of step plays an important role in the flame fluctuation. Finally it is examined systematically that the flame and heat release fluctuation are coupled strongly to the vortex shedding generated by swirl flow and acoustic wave propagation from the analysis of flame-vortex interaction.